What is clay colored stool?
Normally, stool is colored in light to dark brown color. The normal color of the stool comes from chemical substance-bilirubin, which is produced by liver from hemoglobin, after red blood cells have finished their life cycle and die. In case of different pathologies and physiological changes, stool can change its color. This might be a sign of some dietary changes, as well as serious pathology or as a complication to other conditions, like short bowel syndrome.
Clay colored stool is not a normal sign. This means that during the process of stool formation, bilirubin is not present therefore the stool lacks the typical brown color [1,4].
Bilirubin is the breakdown product of heme compounds. 80% of these heme compound come from breakdown of red blood cells, but the other 20% are from different sources, containing heme. In liver and spleen cells, biliverdin is produced from heme, and then it is converted to bilirubin. Bilirubin is hydrophobic, thus insoluble in blood. Bilirubin is transported by Albumin-major plasma protein. Albumin has a high capacity to bind with bilirubin, but there are other substances which can compete with it. These substances include:
- Free fatty acids
- Food additives
After this process, a small amount of bilirubin is excreted in urine (urobilin). The rest of it travels to the liver, where in the hepatocytes it is conjugated with glucuronic acid. This conjugated bilirubin is then excreted in the bloodstream. In the gut, bilirubin is again deconjugated by the bacteria and reabsorbed in the colon .
Since bilirubin is produced in the liver, lack of it can cause loss of color in stool. There are various disorders that can cause disruption of normal physiological processes in the liver. In this case, there will also be increased levels of bilirubin in the blood circulation which may cause fatigue, jaundice- yellowish color of skin and the whites of the eyes.
One of the most common causes for liver disease is hepatitis. It can be either viral hepatitis, or caused by other factors, such as chronic alcoholism. Patient history can be very helpful in determining the type of hepatitis, since viral hepatitis requires contact with another patient, but alcoholic hepatitis patient will have a long history of alcohol use. Symptoms of hepatitis include:
- Dark urine
- Abdominal pain
- Weight loss
- Loss of appetite
- Clay colored stool
- Fatigue [4,5]
Bile duct obstruction
After bile is produced, it goes through a system of bile ducts and is stored in the gallbladder. In case a part of this system is obstructed, the bile does not reach intestines and stool can appear clay colored. There are several causes for bile duct obstruction:
- Biliary atresia- biliary atresia is a congenital defect, and clay colored stool will be present after birth, along with other symptoms [3,4].
Liver cancer is a likely cause for clay colored stool. Liver cancer often develops with time in patients with cirrhosis. Bile duct obstruction can also be caused by secondary liver cancer- metastases in liver from a different cancer.
A very rare entity that can cause clay colored stool is bile duct cancer. Bile duct cancer can occur in either intrahepatic bile ducts or in extrahepatic bile ducts.
Bile flow obstruction can also be caused by late-stage gallbladder cancer.
One of the most common types of cancer to cause bile duct obstruction is pancreatic cancer. When the head of the pancreas gets enlarged, it can cause external obstruction of bile ducts [4,5].
There are some medications that can cause clay-colored stool, such as:
- Isoniazid- used for treating tuberculosis
- Bismuth salicylate- used for treating heartburn, indigestion, nausea and diarrhea. It limits the secretions in the digestive tract and inhibits growth of certain bacteria.
- Kaolin- natural clay used for treating diarrhea
- Barium sulfate-used as a contrast substance for detecting various digestive tract disorders with X-ray [4,7].
In case of clay colored stool, medical attention should be sought. Diagnosing the cause of clay colored stool might include:
- Physical examination and taking patient history
- Blood analysis: complete blood count, liver enzymes, bilirubin levels
- Imaging studies: X-ray, CT, MRI and ultrasound imaging
- Specific tests, for example to detect hepatitis virus A, B or C
- Microbiological tests of the stool
- Endoscopic retrograde cholecystopancreatography [7,8]
The treatment of clay colored stool depends on the underlying cause. If it is caused by use of certain medication, the agent will most likely be changed.
Medication treatment is mainly used for treating hepatitis, as well as therapy for some types of cancer.
If the bile ducts are obstructed, surgery might be necessary to treat the cause .
For your personal experience, use the comments section below.
- Stool color changes: http://www.medicinenet.com/stool_color_changes/page8.htm
- Bilirubin metabolism: http://med.stanford.edu/irt/edtech/video/fall2015auth/html/pdf/inde222-09-29-2015-09-lect-Lowe-1.pdf
- In babies: http://www.hopkinsmedicine.org/health/articles-and-answers/healthy-children/stool-color-guide
- Causes of clay colored stool: http://www.livestrong.com/article/97409-causes-light-pale-feces-/
- Causes : http://www.md-health.com/Clay-Colored-Stool.html
- Medication information: https://www.drugs.com
- Diagnostics: https://medlineplus.gov/ency/article/003129.htm
- Treatment: https://www.verywell.com/what-can-cause-pale-or-clay-colored-stool-1942944